Since an electric motor-driven vehicle, such as an electric vehicle, a hybrid vehicle, a fuel cell vehicle, or the like, does not have an idle torque unlike an engine vehicle, a separate control for creep driving is required.
In addition, when a step control is performed at the time of applying a creep torque, it does not provide comfortable driving feeling. Therefore, filtering allows a torque to be smoothly output to a motor. However, when calculating a time constant for the filtering, determining the time constant of a creep torque control has a following trade-off.
1. The time constant is decreased for a smooth creep start of the vehicle (particularly, in a going-up situation).
2. The time constant is increased in order to decrease rapid acceleration feeling at the time of starting the vehicle and to decrease creep noise at the time of braking the vehicle (particularly, in flatland and going-down situations).
Therefore, the greater the time constant, the greater the amount of sliding at the time of starting the vehicle on a ramp under insufficiency of the creep torque is produced.
The matters described as the related art have been provided only for assisting in the understanding for the background of the present disclosure and should not be considered as corresponding to the related art known to those skilled in the art.